Power supplies for microelectronic devices typically provide regulated power to electrical loads. For example, and with reference to FIG. 1, a typical power supply 10 provides power to load 30 over conducting path 20. Power supplies often include a voltage regulator module or switching power converter (“SPC”). SPC's are commonly used to regulate the input voltage to an electrical load. A well regulated voltage level is very important in devices such as microprocessors, microcontrollers, memory devices, and the like.
Typical microprocessors require stable, low voltage and high current power. For example, emerging microprocessors often run on less than 2 volts and more than 50 amperes. SPC's often utilize step-down Buck converters to meet the low voltage/high current requirements of microprocessors. With reference now to FIG. 2, in a typical step-down Buck converter, a control IC 210 directs the switching of power to an inductor 270 in series with the electrical load 230 and a capacitor 224 in parallel with the electrical load 230. Control IC 210 directs the switching such that a relatively steady voltage level is provided across the load 230. Furthermore, some voltage regulation modules have the ability to selectively vary the steady state voltage level provided to load 230. In this case, the load voltage level and current level are sensed and fed back to control circuit 210 over feedback lines 226 and control circuit 210 adjusts the switching rate of switch 220 to maintain a relatively steady voltage level at the level provided by an input voltage reference signal on voltage reference line 205. The steady state voltage output has a small ripple, fluctuating slightly above and below the steady state voltage value.
As the speed and integration of microprocessors increase, the demands on the power regulation system increases. In particular, as gate counts increase, the power regulation current demand increases, the operating voltage decreases and transient events (e.g., relatively large voltage spikes or droops at the load) typically increase in both magnitude and frequency.
With prior art power regulation systems, a transient current immediately causes the voltage level across the load to change. The control IC eventually compensates for the change in current and returns the load voltage to its proper value, but a droop or spike is observed in the voltage immediately after the load transient. Such a droop or spike is problematic because it may cause the device to lock up or otherwise fail.
FIG. 3 illustrates a typical load voltage regulated using system 200. Voltages across load 230 typically exhibit a voltage ripple 310 during non-transient operating conditions. A transient occurs at time 312 or 322 causing the voltage level to immediately change. This first droop 314 or spike 324 occurs because of the load package parasitics, and may appear for about 10 nanoseconds. The second droop 315 or spike 325 occurs due to board paracitics and typically appears about 150 nanoseconds from the end of the first droop/spike. A third droop 316 or spike 326 appears as a result of the control IC response time.
SPC's are generally configured to eliminate or reduce the magnitude of the third droop/spike by using Active Voltage Positioning (AVP). AVP involves providing an offset to the reference voltage by an amount proportional to the sensed load current, thereby ideally allowing the loop to settle at the peak of the third droop/spike, e.g., 330 or 340. Often, AVP is unable to overcome the third droop/spike entirely due to the magnitude of the current change.
Prior art SPC's have sometimes been able to eliminate or reduce the third droop because the load transitions of the past have been slower. However, as the microprocessor clock speed increases and the board area available for bulk capacitors decreases, the second and third droops are becoming more prominent and the prior art SPC's are less able to compensate for such droops. Various attempts have been made to create systems capable of responding more rapidly to the transients and to eliminate the first, second and third droops/spikes. These attempts have generally not been successful. Inherent delays in detection of the transient and transmission of the detection signal to the control IC are typically too large to address first and second droops/spikes. Furthermore, some existing transient response techniques have been unsuccessful at effectively containing the transient spike/droop and implementing recovery from the transient response mode to the steady state, closed loop operation mode. In extreme cases, not only is transition to the steady state voltage level delayed, but the control IC may fail to regain steady state control of the Buck converter operation. In addition, transient response techniques often run the risk of large heat generation which could result in destruction of the voltage regulator.
Accordingly, an improved power regulation system is needed. In particular, a system including a rapid transient response regulator is desired. More particularly, it is desirable to provide a power regulation system capable of detecting, responding to and recovering from transients to address first, second, and third droops/spikes.